1. Field of the Invention
The present invention relates generally to a fluid-filled tubular vibration-damping device capable of obtaining vibration damping effect based on flow action of the fluid sealed inside. More particularly, the present invention pertains to a fluid-filled tubular vibration-damping device capable of obtaining vibration damping effect against vibration input in the axial direction.
2. Description of the Related Art
Conventionally, a tubular vibration-damping device of fluid-filled type has been used as a vibration damping linkage device, a vibration damping support device or the like mounted between components that make up a vibration transmission system in order to reduce vibration, which is disclosed in Japanese Patent Republication No. JP-B-H2-029899 etc., for example. The tubular vibration-damping device typically includes an inner shaft member and an outer tube member connected by a main rubber elastic body, two fluid chambers provided between the inner shaft member and the outer tube member, and an orifice passage interconnecting the two fluid chambers. During input of vibration, vibration damping effect will be exhibited based on flow action of the fluid induced to flow between the fluid chambers through the orifice passage.
Meanwhile, as disclosed in JP-B-H2-029899, for the tubular vibration-damping device, in order to obtain an excellent vibration damping effect against vibration input in the axial direction, suggested is a structure wherein a partition wall partitioning the two fluid chambers is provided in a movable manner in the axial direction with respect to the inner shaft member.
However, the structure disclosed in JP-B-H2-029899, wherein a resin sleeve bonded to the inner peripheral surface of a partition wall rubber is disposed externally around the inner shaft member in a slidable manner, is complicated and makes the manufacture difficult, since it is necessary to prepare the resin sleeve and bond it to the inner peripheral surface of the partition wall rubber elastic body. Moreover, through the gap between the resin sleeve and the inner shaft member, leakage of the fluid pressure or short-circuit of the fluid are likely to occur between the two fluid chambers, posing a problem of difficulty in obtaining a desired vibration damping ability with stability.
Besides, Japanese Unexamined Patent Publication No. JP-A-S64-035138 discloses a structure including thin, annular seals that project from axially opposite sides of the partition wall rubber so as to be convex peripherally inward in order to seal the gap between the partition wall rubber and the inner shaft member. However, the annular seal disclosed in JP-A-S64-035138 extends in the circumferential direction with an arcuate cross section whose middle portion in the direction of projection is made thick and is made thinner toward its distal end. Accordingly, the annular seal is in contact with the outer peripheral surface of the inner shaft member at the middle portion in the direction of projection whose diameter is the smallest, while its thin-walled distal end portion is remote from the inner shaft member so as to turn up.
Therefore, when the partition wall rubber moves in the axial direction of the inner shaft member, the fluid pressure will act on the inner peripheral surface side of the distal end portion of the annular seal, which is remote from the inner shaft member so as to turn up, so that the sealed state is likely to be broken by the fluid being led into the section where the annular seal is in contact with the inner shaft member. Since it is necessary to establish a large contact force of the annular seal with respect to the inner shaft member in order to maintain the sealed state, the movement resistance becomes large at the contact section of the annular seal with the inner shaft member. Thus, it becomes an issue to address the problems such as deterioration in vibration damping ability, deterioration in durability due to rubbing of the contact section, occurrence of sliding noises, or the like.
Moreover, due to the movement of the partition wall rubber in the axial direction of the inner shaft member during attachment or input of vibration, frictional resistance or fluid pressure will act on the thin-walled distal end portion of the annular seal so as to make it deform to the inner shaft member side, posing a risk that the distal end portion may be inserted further into the inner peripheral surface side of the partition wall rubber from the contact section of the annular seal with the inner shaft member, so as to be jammed between the partition wall rubber and the inner shaft member. Then, if the distal end portion of the annular seal is jammed between the partition wall rubber and the inner shaft member, the annular seal gets damaged and the desired vibration damping ability will not be exhibited, causing loss of product life.